The present disclosure is related generally to the field of dental treatment. More particularly, the present disclosure relates to modifying digital images of teeth to improve fit of dental appliances made using the images.
Dental treatments can involve repositioning misaligned teeth and changing bite configuration for improved cosmetic appearance and dental function. Orthodontic repositioning can be accomplished, for instance, through a dental process that uses one or more removable tooth-positioning appliances for realigning teeth.
Such appliances may utilize a shell of material having resilient properties, referred to as an “aligner” that generally conforms to a patients teeth but is slightly out of alignment with the then current tooth configuration. Placement of an appliance over the teeth can provide controlled forces in specific locations to gradually move the teeth into a new configuration. The appliances can be semi-rigid, allowing for flexing of the appliances as the appliance is placed over the teeth of a patient.
Placement of the appliance over the teeth can be affected by an undercut area of a tooth of a patient. An undercut area of a tooth can include an area of a tooth below a widest part of the tooth, which may or may not be the height of contour of a tooth depending on the orientation of the tooth in the jaw, and extending toward the gingival line of the patient. In some instances, it can be difficult for a patient with insufficient or excessive undercut areas to secure the appliance over their teeth. For instance, an appliance placed on teeth of a patient with insufficient undercut areas may slip off the patient's teeth in an undesirable fashion and/or at undesired times; and, an appliance placed on teeth of a patient with over-sufficient undercut areas may be extremely difficult to insert causing great discomfort and/or distortion in the appliance. How well an appliance is seated on the patient's teeth can be referred to as the degree of fit of the appliance. For situations with excessive undercuts, it may be possible to fill an undercut area of a tooth with a filler material prior to the impression of the teeth and/or by blocking out the reference on the dental mold during the appliance fabrication process, so that the fit of the appliance is improved (e.g., improving the retention of the appliance onto the number of teeth). For insufficient undercuts, artificial undercuts may be created by trimming away parts of the reference model and/or by physically creating undercuts on the teeth. In any case, what is typically assumed is a single path of insertion (e.g., line of draw and/or axis of placement) and removal for a single appliance. In the event of a rigid appliance, only a single path of insertion can exist. However, for semi-rigid flexible appliances, multiple paths of insertion and removal can exist, or at least difference paths of insertion and removal for different portions of the appliance.